Fluid pressure gauge



SePf- 9 1947 G. c. R. BIRCH v .2,427,249

l FLUID PRESSURE GAUGE' Filed Sept. 14, 1944 2 Sheets-Sheet 1 E/ G/ E G4 E3 "GG A, E2 4 B l 3 E5 l G 2 l I M4 E K L L i2 G2 Kl M J/ O Q l2 J3 s `o F133 M3 J G2 F B' K3 M EE? 3 L/ E4 l G G G4 G5 G GEbnE C. R. 5 [RC lInval-127;);-

Attorngy l Sept. 9, 1947. G. c. R. BIRCH 2,427,249

` FLUID rREssURE GAUGE y Filed spt. 14, 1944 z-sheets-sheet 2 Attorney Patented Sept. 9, y 1947 George Christian Ross Birch,

' lanLy f :assigner `vrto 11B. & fR. j fPatents, lI'limited, LondongrE-ngland, fa eompanyr offGreatz Britain mlApplication"September 14, 1944,'"SerialfNm554J Y LIn'Greatiritan@June *5,1944

e 1 'lhiseinventionmlates ltodiierential uidrpressure' gauges :of the @kind `feompris'ing ',two pressure Vresluon's'ure .elementsrsuch for Vy,example as expansble bellows, reach :comprising .an zabutment mounted nneaxbase and iawzpartmovable relal tively 'to fsaidabutment :under the :appliedifluid pressure, theflwo pressure responsive :elements being ;simultaneouslyf` 'subject to two pressures resneetiuelysthe Idiiferenee .betweenfwhch is :indieated fon ithe. gauge by suitable Vindicating means. y

',{Ehezginventionhas-"for its object tto provide :an impmyedyeonstructi'on of sucngauge which,-.while capable .of'withstan'ding high-.nuidzpressures -will perm-ity theuusezof :riel'atively r'light epressure responsive: elements tand yindicating vmeciianism 'so as to ensure:accurate:andfsensitivexresponse vand indleationuln'oughoutthemangeofmeasurement othe gauge. v

Y 1.511" a'ifluidpressure gauge according toithe i invention, `:the ianovable parts `:offthe 'pressure responsive elements :are loaded by atspring inger orfrodmnchored iozthebase; ithezmdicating mechanismlfbeing actuatedin `aeiznrdanee ',with lthe degreesnf exurenf'the'spring rod in one :directionmtheother.

Rteferablyfthe rmovablerparts cof fthe-two pressure :responsive `elements:are connectecliy together and :to the ree send portiono'f Athe .spring rod `by a singlelcouplinglrdevice extending"stransversely to rthelength lof thefspring'frod. Means fare convenientlyzprovided Jfor r:adjusting 7at* :least .zone ofith'efpressure :responsiveelementsl so :as fto :Vary itslinit'ial:stiffnessmrrate Tor example, the coupling device may be longitudinally adjustablexso asllto'mary3the1initia1itension ior rate'iof :both/the pressure nresponsiv'e elements. In afpreferred construction theepressure fresponsivefelements are constituted fby :twoexpansible Lbellows :arranged mthdaheirjongitudinalzaxis:substantially in :alignmentpand smeans are L.pu'ovicted for adjusting'the abutment @surface between :at zleast tone kof the abutments and'ilthe:corresponding bellows in a directirtransverse'to'the saidwaxis. Y.

'Ilheziindi-catingi mechanism rmayirbe :operated by aleverfnivoted enithelzbase and aetuatedfrpreferably Iadjacent vto `:its apivot, :"by a part `moving Withtheifree: end fofrthe: springfrod,tmeansfbeing conveiently provided ffforgaijusting thefidistance betweenl'theLpivotbfltheileverrand the point of engagement between the Elever and `lthe :sp1-ing rod. For example, the said pivotedaleuerimay be operatedrby aglugiorl elawsformedjntegral-with the free end of the spring itoLetheeleverfbeing conytenientiy .fbiassed :by fa light 1spring :into en- L2 gagement with the lug or claw. In orderitoravoi'd damage .to 'the gauge :due 'to.'overload,` eae'hpressurefzresponsive element may abe furnished Lwit'l'i fa' stop which :automatically limits :the range :of actuationnf'the'element.

:Theinvention be `merriediintolpractiee in various aways but sone construction :aecordingr'to invention is-shnwn dayfwayso'f example inthe 'accompanyingadrawingsgmfwhich Figure elfis5a planiofithe gauge lwitlithereover lixlate7 dialandapointeriremoized, [Figure iisv '.a verticalaseetion 'with the cover plate'dakmidnpointer imposition, f

Viguivei 3 .illustrates "tire :adjustable :coupling betweenthe'-twoi'bellows,

' Eigure :4 :showsithe fendp'ieee fof :one `fbellmvs in enidf elevationi'andwith the associatedkv nutk remouedand Eigure a5 :Lis llongtudinaliseetion :through :one of the bellows but with the envelope omitted.

In-the :construetizonshown ein iythe drawings the gauge :comprises-ea flat :metal base A .having '-.an upstaniiingzcylindreal ange Ali'formed integral therewith,A and icons'titutingithe main :casing of the gauge. -`nlilxtending upwards-from :the ibase within the Leasing areatwo vertical rpillarsrB :each hav-ing threaded aperture sin fits :upper'fend'for receiringia lgrub.fscrewwiil'iereby.aiial C, suitably graduated,Vaisseounedin pesitionfsolastoiielupon the 'annu-lar upper ledge :of *the cylindricalfeasirrg Al. f L eimetalbezeleDflies :Ourthe-upper -surfacefo'f the dial-E 'andithe usual mrctective glass DI is presentedidown enso ftthefhezeldzby acylindrieal metal :caprfDZ zsecuned toithe .cylindrical .wall :A1 of thercasingby screws lA2.

:Arranged rwithin the cylindrical :casing A1 :are twopressure uesponsiue elements which maybe as :shown eachfimthefformofsan expansblefspring hallowed-EVE.1 :and fcomprisng la xed part 'or abutment'lEzooperating f with a bracket whose upwardly; extending apart :has anopening Tcoaxi-al :with the lbellowsfwhlst iits lower apart or foot Ei is secured dio thebase .-A of fthe easing. llhe two lbellows LE, E1':a1e opposed, thatfis-'to they lie r,with their .axesfsubstantially in falignment, and ithe adjacent =or .freeends .E5 of the bellows, which iconstitute tire mmvable parts thereof @are secured :together lby .a longitudinally adlustablef-.coupling :deviwcel` comprising la fbifunca-ted plug TF1 carried fby the :movable part of onegibellows and y.awtonsule `:or ld'og F2 carried Aby the nuova-ble part-,cf the'fother'bellowsandmaking a sliding fit into the slot of the said plug F1... lThe biiurcated plugrFl LarsetascrewzFafwhereby the deg :Fig .fandnbfmfeated-- plug- ;E'l can uhe lonken in the desired position of relative adjustment. In this way, the effective length of the coupling device F, and therefore the initial tension or rate of the two bellows E, E1 can be set as required.

The fixed end E2 of each bellows is closed by an end piece furnished with a screwthreaded nipple G1 which extends through the opening in the upwardly directed part E3 of the associated bracket, a flanged nut G4 being screwed to the nipple G1, on that side of the bracket remote from the bellows, for securing in position the adjacent end of a capillary tube G through which the fluid pressure is applied to the interior of the corresponding bellows. The two capillary tubes G lead to two screwthreaded pipe connectors G2 carried by an arcuate plate G3 secured to the outer surface of the cylindrical casing A1 which has a suitable slot or opening A3 in its wall to accomm-odate the two pipes G extending therethrough.

The opening H in the upwardly directed part E3 of one (or of each) of the brackets is elongated as shown in Figure 4 or is enlarged relatively to the diameter of the nipple G1 extending therethrough, so that by easing the associated anged nut G4 the end piece E2 of the bellows can be adjusted about the axis of the set screw F3 thus slightly altering the volume of the bellows E and thereby aording a ne initial adjustment to compensate for any dilerence between the elective fluid pressure areas of the two bellows. To facilitate this adjustment of the abutment surface between the xed abutment, constituted by the bracket E3, and the cooperating bellows, the corresponding capillary tube G may be furnished with a curl or loop G5 which will alford the resilience necessary to permit the slight translational adjustment of the associated end piece of the bellows.

Extending, at one end, through an aperture in a vertical pillar J1 carried by the base A between the capillary tubes G where these extend through the opening A2 in the wall A1 of the cylindrical casing, is a spring rod J whose other or free end extends transversely through the part of the coupling device F having the tongue' F2 and carrying a set screw F4 whereby the spring rod J can be securely locked to the said coupling device, A similar set screw J2 locks the fixed end ofy the rod J in the aperture of the anchorage pillar J1. That end of the spring rod J which projects from the side of-the coupling device F remote from the anchorage of the rod is bent downwardly to constitute a lug or claw J3 which lies to one side of a lever K pivoted at K1 on a bracket K2 carried by the base A, the lever K extending from the pivot K1 and beneath the coupling device F back to a point adjacent to the anchorage pillar J1 of the spring rod J. A light spring K3 anchored at one end to the base at K4 is connected at its other end to the pivoted lever K so that this is lightly biassed into engagement with the claw J3 at the free end of the spring rod J. The claw J3 thus engages the pivoted lever K near the pivot vor fulcrum K1 thereof so that any movement of the free end of the spring rod J, that is to say movement of the coupling device F due to expansion of one bellows relatively to the other with consequent corresponding ilexul'e of the spring rod J, will be represented by a somewhat magnified movement at the end of the pivoted lever K.

By releasing the set screw J2 on the anchoring pillar J 1 the spring rod J can be longitudinally ad,-`

4 justed so as to increase or decrease the distance between the pivot K1 of the lever K and the point where the claw J3 of the spring rod J engages the lever K, thus decreasing or increasing said magnification.

Mounted on a plate L supported by two subsidiary pillars L1 disposed between the pillars B carrying the dial C, is a movement frame M which carries the indicating mechanism comprising a central rotary shaft M1 furnished with a toothed drum which is engaged by a toothed quadrant M2 pivotally mounted on the movement frame M and operated, through a light link M3, by a U- shaped bracket M4 carried by the end of the pivoted lever K which lies beneath and extends beyond the movement plate L.

In operation the two pipe connections G are coupled to the two fluid pressure sources whose diierence is to be gauged, the initial tension of the two bellows E, El having been set as desired byV means of the coupling device F, whilst such relative compensation as may be required is effected by transverse translational adjustment of one xed abutment surface E2 as above described. As the pressure applied to one bellows increases relatively to that applied to the other bellows the spring loading rod J will be correspondingly ilexed so that ther pivoted lever K will be turned about its pivot K1 either by the direct action of the claw J3 on the spring rod J or by the biassing spring K3 according to the direction of iiexure of the loading spring J. The resultant angular movement of the lever K will turn the toothed quadrant M2 and thus rotate the central rotary shaft M1 which extends freely through a central aperture in the dial C and is secured to a pointer N lying above the upper surface of the dial C.

'It will be appreciated that since movement of the coupling device F from a central or static position can only take place against the pressure of the spring loading rod J, which is preferably made from a length of steel rod and aiords a high rate of increase in the loading for a small movement of the coupling device F, the inherent resistance of the pressure responsive elements E, E1 need not exceed that necessary for light uid pressure loads even though the gauge is capable of dealing with high fluid pressures on either pressure responsive element. Thus, a high fluid pressure rating is obtained for the gauge whilst permitting the use of light pressure responsive elements and indicating mechanism associated therewith so as to ensure accurate and sensitive response and indication throughout the range of measurement of the gauge.

It will be understood that the constructiOn above described is given by way of example only and that details may be modiiied to suit requirements. For example, in spite of the high rate of increase of the spring loading afforded by the spring rod, it may be preferred to guard against accidental overloading by providing each pressure responsive element with an overload stop which limits the range of movement of the movable part relatively to the fixed part or abutment thereof. As shown in Figure 5, such stop may comprise an internal longitudinally radjustable hollow distance piece P carried by the end piece E2 of the bellows and cooperating with a stop P1 at the other or movable end E5 of the bellowsv to provide a positive limit to the range of expansion of the bellows.

What I claim as my invention and desireA to secure by Letters Patent is:

,1. A differential fluid pressure gauge compris- S -1ng-:abase,rtwoip1:essurerespionsiveselements each zinclimingr ansabutnrent'zmeunted onethezbasezanrl :a .partrmovable relativelyctotlreabutmentzunder rtrrefnppliedru'rdfpressuregqneanswhereby the ctrworpressureresponsive f eie'ments :are simultanemusly :subiectuan -two pressures respectively, vthe ssaidzfmovable iparts zzo'f zth'e pressure: l'responsivle elements acting in oppositionLtofeachnther, .a springirodfancliored 1 to--s-aidlbase fzmd iresiliently resisting the movement of said movable parts of the pressure=responsive-=elements resultant from .the two..pressures, and. indicating-mechanism actuated in accordance with .the iflexure of the spring rod in one direction or the other.

2. A differentialifluidlpressuregauge comprising 4a base, two opposed pressure responsiveszeleanents each ihaving aneabutment unountedionthe doase andearpart movable rela-tively to thei-abutment :runder .the applied fluid ,-pressurepme'ans wvherebyithe two pressureresponsive elementsa're 'simultaneously subject to :twoiiuid pressuresjthe two movable parts acting in opposition to each other, a spring rod anchored to said base and extending between and transversely to the direction of movement of the two movable parts which thus iiex the rod in accordance with the difference between the said two iiuid pressures, and indicating mechanism actuated in accordance with the flexure of the spring rod in one direction or the other.

3. A differential pressure gauge, as` claimed in claim 1, in which the movable parts of the two pressure responsive elements are connected together and to the free end portion of the spring rod by a single coupling device extending transversely to the length of the spring rod.

4. A differential fluid pressure gauge as claimed in claim 2, in which the movable parts of the two pressure responsive elements are connected together and to the free end portion of the spring rod by a single coupling device extending transversely to the length of the spring rod.

5. A differential pressure gauge comprising a base, two expansi'ble and opposed bellows each abutting at one end against a part carried by the base and having its other end movable relatively to the abutment under the applied uid pressure, means whereby the two expansible bellows are simultaneously subject to two different pressures, the two movable parts of the bellows acting in opposition to each other, a spring rod anchored to said base and extending between and transversely to the direction of movement of the two movable parts which thus flex the rod in accordance with the difference between the two fluid pressures, and indicating mechanism actuated in accordance with the flexure of the spring rod.

6. A diierential pressure gauge as claimed in claim 5, in which the movable parts of the two bellows are connected together and to the free end portion of the spring rod by a single coupling device extending transversely to the length of the spring rod.

7. A diierential pressure gauge as claimed in claim 5, having means for adjusting at least one of the bellows so as to vary its initial stiffness or rate.

8. A differential pressure gauge as claimed in claim 1, in which the two movable parts of the pressure-responsive elements are connected together and to the free end portion of the spring rod by a single coupling device which is longitudinally adjustable so as'to vary the initial tension of both pressure-responsive devices.

. ;9`..:A;.'diierientialfpressuregauge sasfrelaimedain 'mlaim inwhichtlthe *movable parts 'lof Sthe two bellowszare: connected together-zand to fthe free endtporti'ondfltlfie spring rodifby afsingle coupling device fextending Iztrarrsversely: tot :the length of )ether spring trod, the eouplingfdevice yib eing zlong'i- 'tudinaiiyeadjustab'lefsoasdo ivarythe l initial stensinnnnbotl'rbell'ows .'10'.; A1 differential prtessuregaugezascclaimediin claim r 5;:in "/which ithei two bellows sare arranged :ineaxialialignment and 'meansffare provided Safor eeiecting .relativeadjustment between at least'fone fof rtlreziiellowsrfand iitsabutment-m sa =..direction :transverse 'to-:the axis ofthe bellows.

11. Andifferential fpressureigaugezas :claimedrin claim 15 -in which the @two bellows fare arranged in taxial alignment .imea'ns being "providedsifor r-eectingrelativefadjustmentzloetweerr atleast-.one

of `the bellows fand its Aabutment .in a .direction transverse .to-,fthe waxes-:of the vbeliows,v and-:the .movable :part-s of the rtwo bellows .fare rconnected together and to the free end portion of the spring rod by a coupling device extending transversely to the length of the spring rod, the coupling device being longitudinally adjustable so as to vary the initial tension of both bellows.

12. A differential pressure gauge as claimed in claim 1, in which the indicating mechanism is actuated by a lever pvoted on the base and actuated -by a part moving with the free end portion of the spring rod.

13. A differential pressure gauge comprising a base, two expansible and axially aligned bellows each abutting at one end against a part carried by the base and having its other end movble relatively to the abutment under the applied fluid pressure, means whereby the two expansible bellows are simultaneously subject to two fluid pressures from different sources, the movable parts of the bellows acting in opposition to each other, a spring r-od anchored to said base and extending between and transversely to the direction of movement of the two movable parts which thus rlex the rod in accordance with the difference between the two fiuid pressures, a lever pivoted on said base, a part moving with the free end portion of the spring rod and acting transversely on the said lever at a point spaced from the fulcrum thereof, and indicating means actuated by the free end portion of said lever.

14. A differential pressure gauge as claimed in claim 1, in Iwhich the indicating mechanism is actuated by the free end portion of a lever fulcrumed on the base and acted upon by a part moving with the free end portion of the spring rod, means being provided for adjusting the distance between the fulcrum of said lever and the point of engagement between the lever and the part carried by the spring rod.

15. A diierential pressure gauge as claimed in claim 13, in which means are provided for adjusting the distance between the fulcrum of the lever and the point of engagement between the lever and the part moving with the spring rod.

16. A differential pressure gauge as claimed in claim 1, in which each pressure responsive element is furnished with a stop which automatically limits the range of actuation of the element.

17. A diierential pressure gauge as claimed in claim 5, in which each bellows is furnished with a stop which automatically limits the range of actuation of the element.

18. A differential pressure gauge comprising a base, two expansible bellows in axial alignment,

each bellows acting at its outer end on an abutment carried by the base and having its other end free to move axially relatively to the abutment under the action of the fluid pressure applied to the interior of the bellows, the two movable inner or adjacent ends of the bellows thus acting in opposition to each other,'a spring rod anchored at one end to the base and having its free end portion extending between and transversely to the expanslble bellows, a coupling device connecting the movable ends of the bellows together and to the free end portion of the spring rod, means for adjusting the effective length of the coupling device, means for adjusting at least one of the bellows relatively to its abutment on the base transversely to the axes of the bellows, a lever fulcrummed at one end on the base, a transverse projection at the free end portion of the spring rod and acting on the lever adjacent to said fulcrum, an indicator operated by the free end portion of the lever,`a spring acting on said lever and tending to urge it into engagement with said transverse projection, means for REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,296,947 Blot-Garnier et al. Mar. 11, 1919 1,416,210 Jung et al May 16, 1922 1,954,425 Place et al. Apr. 10, 1934 2,072,916 Willach et al Mar. 9, 19,37 2,268,469 Barnhart Dec. 30,1941 

